For use in liquid crystal display (LCD) applications it is often required to have available liquid crystal (LC) compounds and media with a high positive value of the dielectric anisotropy Δε, which in turn requires that the material has a large molecular dipole. Until now, materials with terminal cyano groups have been used extensively for this purpose, as the cyano group is of high polarisability.
Thus, LC compounds with a Δε of +20 or more and having a terminal cyano group are widely known in prior art. For many applications, however, LC compounds and media with still higher Δε are needed. Furthermore, the compounds known from prior art do often have unfavourable properties, like high melting points, smectic phases or unfavourable vaues of the birefringence.
Consequently, there is still a need for materials with high polarity and positive Δε that can be used in LC media to increase the value of Δε, without negatively affecting the other properties of the media, such as the LC phase range.
The inventors of the present invention have found that the above mentioned drawbacks can be overcome by providing cyanopyridone derivatives as claimed in the present invention. These compounds have advantageous properties and are suitable for use in optical, electrooptical, security, electronic, charge transport, semiconductor, optical recording, electroluminescent, photovoltaic or electrophotographic applications, in particular in LC media and LC devices.
WO 88/07992 describes 5-cyano-1,6-dihydro-6-oxo-2-(4-octyloxyphenyl)-pyridine as intermediate in the preparation of cyanopyridines for ferroelectric LC media.
EP 0 180 188 describes the use of 3,4,5-trimethoxybenzoic acid 5-cyano-1,6-dihydro-6-oxo-2-pyridinyl ester for use in pharmaceutic compositions to increase the anticancer activity of 3-fluorouracil and related compounds.
DeJohn et al., J. Heterocycl. Chem. 1983, 20(5), 1295-1302 describe 5-cyano-1,6-dihydro-6-oxo-2-[2-(4-methoxyphenyl)ethenyl]pyridine. Rateb et al., J. Chem Soc. 1960, 1426-1430 describe 3-cyano-1,2-dihydro-6-(4-methoxystyryl)-2-oxo-isonicotinic acid ethyl ester and its substituted derivatives.
One aim of the present invention is to provide novel cyanopyridone derivatives with improved properties, especially mesogenic or liquid crystalline cyanopyridones with a rod-shaped molecular structure and polymerisable cyanopyridones.
Another aim is to provide advantageous uses for the novel cyanopyridone derivatives, such as liquid crystal media, liquid crystal devices, anisotropic polymers, optical, electrooptical, decorative, security, cosmetic, pharmaceutic, diagnostic, electric, electronic, charge transport, semiconductor, optical recording, electroluminescent, photoconductor and electrophotographic applications.
Another aim of the invention is to provide improved LC media and LC polymers with high polarity and high positive values of the dielectric anisotropy that do not have the drawbacks of LC media known from prior art.
Other aims of the present invention are immediately evident to the person skilled in the art from the following detailed description.